1. Field of the Invention
The present invention relates to a variable reluctance-type resolver.
2. Description of the Related Art
As a rotation detecting sensor, resolver including coils has been known. For example, variable reluctance-type resolver disclosed in the Japanese Patent Laid-open Publication No. 2002-168 652 comprises a stator on which an excite coil (winding), first detect coil (winding) and second detect coil (winding) are wound, and a rotor having four arch-shaped induct portions protruded radially outwardly.
When the rotor rotates, gap between the induct portions of the rotor and the magnetic poles of the stator on which the coils are wound varies. This gap variation is detected as variation of the reluctance, through the excite signal exciting the excite coil and output signal inducted by the detect coil by a magnetic flux generated by the excite coil. The reluctance variation is detected as rotate angle of the rotor.
In the above variable reluctance-type resolver, when a member made of a magnetic material is disposed near to the rotor, there is fear that a part of the magnetic flux generated by the excite coil flows into a magnetic member disposed near to the rotor. Thus, leakage of magnetic flux may occur. As the magnetic member disposed near to the rotor, a stopper for fixing the rotor to a rotate shaft can be illustrated.
If the magnetic flux leakage occurs, the output signal is not inducted (induced) in the detect coil of the stator accurately, which makes accurate detection of the reluctance variation difficult. In this way, the detect accuracy may be deteriorated. To avoid the magnetic flux leakage, the stopper can be made of a non-magnetic material through which the magnetic flux hardly passes. However, the non-magnetic member more expensive than the magnetic material increases the cost.